Abstract
Long-term continuous groundwater level and land subsidence monitoring in the Houston-Galveston area indicates that, during the past two decades (1993–2012), the groundwater head has been increasing and the overall land subsidence rate has been decreasing. Assuming that the hydraulic head in the aquifer will reach or exceed the preconsolidation level in the near future, will subsidence in the Houston-Galveston area eventually cease? The key to answer this question is to identify if there is deep-seated subsidence in this area. This study investigated the recent subsidence observed at different depths in the Houston-Galveston area. The subsidence was recorded by using 13 borehole extensometers and 76 GPS antennas. Four of the GPS antennas are mounted on the deep-anchored inner pipes of borehole extensometers. We conclude that recent subsidence (1993–2012) in the Houston-Galveston area was dominated by the compaction of sediments within 600 m below the land surface. Depending on the location of specific sites, the compaction occurred within the Chicot aquifer and part or all of the Evangeline aquifer. No measurable compaction was observed within the Jasper aquifer or within deeper strata. Deep-seated subsidence is not likely occurring in the Houston-Galveston area.
Highlights
The Houston-Galveston area provides one of the most extreme case studies of subsidence hazards, which is a problem that affects many other U.S metropolitan areas, for example, Los Angeles (CA), Sacramento (CA), New Orleans (LA), Phoenix (AZ), and Tucson (AZ) [1,2,3]
Holzer and Bluntzer [8] studied subsidence profiles across 29 oil and gas fields in Houston, Texas, from 1943 to 1973. They concluded that the contribution of petroleum withdrawal to local land subsidence is relatively small compared to aquifer compaction
This investigation indicates that the recent subsidence (1993–2012) in the Houston-Galveston area is dominated by the compaction of aquifers associated with groundwater withdrawals
Summary
The Houston-Galveston area provides one of the most extreme case studies of subsidence hazards, which is a problem that affects many other U.S metropolitan areas, for example, Los Angeles (CA), Sacramento (CA), New Orleans (LA), Phoenix (AZ), and Tucson (AZ) [1,2,3]. From measurements recorded by 13 extensometers and 72 GPS stations in the Houston-Galveston area, we derived the average subsidence rate (mm/year) in this area from 2006 to 2012 (Figure 1) The recent (2001–2012) subsidence rate at the Addicks site has declined to less than 1 cm/year from previous 4 cm/year (1974–2000) (Figure 4(a)) Compaction at this site will continuously occur as long as the groundwater head remains below the preconsolidation level (a critical value below which inelastic compaction of the fine-grained deposits occurs) within the aquifer systems in this area. The goal of this study is to explore if deep-seated subsidence is occurring in the Houston-Galveston area
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